Magnetic recording continues trend toward higher recording densities, with magnetic recording densities having already reached 500-600 Gb/in2 using traditional perpendicular magnetic recording technology. Energy assisted magnetic recording (EAMR) is used to further increase magnetic recording densities.
FIGS. 1A and 1B respectively depict top and side views of a portion of a conventional energy assisted magnetic recording (EAMR) transducer 102. For clarity, FIGS. 1A and 1B are not to scale. The illustrated EAMR transducer 102 may be used in writing a recording media (now shown) and typically receives light, or energy, from a conventional laser (not shown) when performing such write processes.
As shown, the EAMR transducer 102 includes a conventional waveguide 110 having cladding 114 and 116 and core 118, a grating 106, a near-field transducer (NFT) 104, a coil 108, and a pole 112. Generally, light from a laser (not shown) is incident on the grating 106, which couples the light to a waveguide 110. Light is guided by the waveguide 110 to the NFT 104 near the air-bearing surface (ABS). The NFT 104, in turn, focuses the light to a magnetic recording medium, such as a disk.
During operation, light from the laser is received by the EAMR transducer 102 through the grating 106, where the waveguide 110 directs light from the grating 106 to the NFT 104. The NFT 104 focuses the light from the waveguide 110 and heats a small region of the magnetic recording medium. The EAMR transducer 102 magnetically writes data to the heated region of the recording media by energizing the pole 112 by way of the coil 108.
When conventionally fabricating a writer pole such as the pole 112, the seed milling process involved during fabrication may be difficult to perform due to the writer pole being built on a bevel. An example of this is shown in FIG. 2, which provides a tilted scanning electron microscope (Tilted-SEM) image 200 of an exemplary pole that is plated on a bevel 202 with height of 500 nm and an angle of 35 degrees. While seed material used during fabrication may be fully removed at the bottom 204 of the bevel 202, full removal of seed material remaining on the slope 206 of the bevel 202 usually requires a seed milling process. Unfortunately, based on such factors as angle of control, mill power, and mill time, the seed milling process performed may result in adverse, over milling of the write pole.
Consider for example where a 30 nm seed layer is used in conventionally fabricating. A seed milling process having a mill time of 240 s at a mill power of 407 W (e.g., including 60 s 10 degree mill and 180 s 75 degree mill) is typically required for full removal of the 30 nm seed layer. While this amount of mill time and mill power would usually result in the removal the 30 nm seed layer, it would also result in a certain amount of over mill at the bottom of the pole. Though the resulting over mill would typically be tolerable for pole fabrication based on an Alumina platform, such results would be intolerable for pole fabrication based on a SiO2 platform. Based on SiO2's mill rate, which is generally 2-3 faster than that of Alumina, a mill time of 240 s at a mill power of 407 W would likely cause undesirable over milling at bottom of the pole and may even lead to core damage (e.g., damage to the core 118).